Low-field MRI Of human lungs with hyperpolarized gas

肺的健康功能依赖于充分和通畅的通气、分布的血液灌注和有效的气体交换。不幸的是，肺功能的高分辨率空间量化已被证明是困难的。超极化气体磁共振成像已被证明在成像肺通气和结构的效用。最近，利用气体磁化弛豫速率（1/T1）对氧的依赖性来提取局部肺泡氧浓度。此外，在屏气期间观察到这种松弛率降低，揭示了血液的氧摄取。区域摄氧量图是可行的，这种技术。不幸的是，低信噪比限制了他们技术的精度。由于肺部的磁不均匀性将横向极化时间T2限制为10 ms，因此必须最大限度地减少每个图像中不可再生磁化损失的量。我们建议通过利用在低成像场（BO）下可用的非常长的横向极化时间（T2约1秒）来提高肺部摄氧量测量的灵敏度。我们描述了一个成像序列，类似于驱动平衡傅立叶变换（DEFT），它利用完整的磁化测量，但恢复到纵向后，每个图像。我们估计这个序列提供了一个数量级的信号强度的改善。新罕布什尔州大学的核物理小组是核科学和MRI用超极化气体生产技术的先驱。我们建议实施新的想法，一个实用的高容量源超极化氦。我们还建议改进我们现有的内部低场成像仪，以实现噪声系数中的主体噪声。利用我们的低场成像仪，气体极化能力，我们打算绘制肺部的局部氧摄取分布。我们的成像仪的开放几何结构还允许研究身体取向对肺结构、通气和氧摄取的重力效应。

Healthy function of lungs relies on full and unobstructed ventilation, distributed blood perfusion, and efficient gas exchange. High-resolution spatial quantification of lung function has unfortunately proven difficult. Hyperpolarized gas magnetic resonance imaging has demonstrated utility in imaging lung ventilation and structure. More recently, the dependence of the gas magnetization relaxation rate (1/T1) on oxygen was exploited to extract local alveolar oxygen concentration. Furthermore, this relaxation rate was observed to decrease during a breath hold, revealing oxygen uptake by the blood. Regional maps of oxygen uptake are feasible with this technique. Unfortunately low signal-to-noise limits the precision of their technique. Because magnetic inhomogeneities in lungs limit transverse polarization time T2 to 10 ms, they must minimize the amount of non-renewable magnetization lost in each image. We propose to improve the sensitivity of measurements of oxygen uptake in lungs by exploiting the extraordinarily long transverse polarization time (T2 approximately 1 second) available at low imaging field (BO). We describe an imaging sequence, similar to driven Equilibrium Fourier transform (DEFT), which utilizes the full magnetization for measurements, but restores it to the longitudinal direction after each image. We estimate this sequence provides an order of magnitude improvement in signal strength. The Nuclear Physics Group at the University of New Hampshire is a pioneer in the technology for production of hyperpolarized gas for nuclear science and MRI. We propose to implement new ideas for a practical high-volume source for hyperpolarized helium. We further propose to improve our existing in-house low-field imager to achieve body-noise in dominance in the noise figure. With our low-field imager, gas polarization capability, we intend to map the regional oxygen uptake distribution in lungs. The open geometry of our imager also allows studies of gravitational effects of body orientation on lung structure, ventilation, and oxygen uptake.